Drawing of thermoplastic synthetic linear polymeric thread and localizing the neck portion of the thread

ABSTRACT

A process for drawing a thermoplastic synthetic linear polymeric thread which comprises feeding the thread to a drawing zone; subjecting the thread to an axial load in the drawing zone whereby the thread necks down and is permanently deformed to form a neck portion therein; localizing the neck portion of the thread in the drawing zone and discharging the thread from the drawing zone. The neck portion in the thread is localized by measuring the temperature of the thread at the point where the neck portion is desired to be positioned, and when the neck portion moves away from its desired position, by changing at least one process parameter that affects the position of the neck in response to the temperature measurement so that the neck portion is caused to return to its desired position. Also an apparatus for carrying out this process and the resulting drawn thread are disclosed.

May 2, 1972 SEMPEL 3,660,550

DRAWING OF THERMOPLASTIC SYNTHETIC LINEAR POLYMERIC THREAD AND LOCALIZING THE NECK PORTION OF THE THREAD Filed 001;. 7, 1969 FIG. I.

ljL 2 4 FIG. '2.

I NVENTOR H E N DRINUS SEMPEL United States Patent 1 Int. Cl. B29c 17/02; B29d 23/13; G0lk 13/06; G01n 25/00 US. Cl. 264-40 3 Claims ABSTRACT OF THE DISCLOSURE A process for drawing a thermoplastic synthetic linear polymeric thread which comprises feeding the thread to a drawing zone; subjecting the thread to an axial load in the drawing zone whereby the thread necks down and is permanently deformed to form a neck portion therein; localizing the neck portion of the thread in the drawing zone and discharging the thread from the drawing zone. The neck portion in the thread is localized by measuring the temperature of the thread at the point where the neck portion is desired to be positioned, and when the neck portion moves away from its desired position, by changing at least one process parameter that affects the position of the neck in response to the temperature measurement so that the neck portion is caused to return to its desired position. Also an apparatus for carrying out this process and the resulting drawn thread are disclosed.

This invention relates to a process for drawing a thermoplastic synthetic linear polymeric thread, in which the thread is subjected to an axial load in a drawing zone such that the thread necks down and is permanently deformed, the neck portion formed in the thread is so localized in the drawing zone that thread breakages are reduced, and the thread is discharged from the drawing zone, and to the drawn thread produced thereby.

The term thread as used throughout this specification is meant to include thread-shaped, ribbon-shaped or the like fibrillary products.

A process similar to this invention is known and described in the British patent specification No. 543,466. In this known process the thread in the drawing. zone is wrapped at least one complete turn round a friction member, in the form of a non-rotatable draw pin, which localizes the neck portion of the thread. At the draw pin the tension in the thread becomes high enough to cause plastic deformation, so that over a relatively short piece-herein referred to as the neck-th-e transverse dimensions of the thread are changed considerably.

However, if the speeds applied to the thread are high, then the use of a draw pin often leads to thread breakage. On the other hand, drawing in the absence of a draw pin may cause the neck portion to be displaced to either of the rolls between which the thread is drawn. This arrangement also involves the risk of thread breakage.

Advantageously, the above-mentioned drawbacks are obviated by the process of this invention. This invention thus contemplates a process which comprises feeding a thermoplastic thread to a drawing zone, subjecting the thread to an axial load in the drawing zone whereby the thread necks down and is permanently deformed to form a neck portion therein, localizing the neck in the thread in the drawing zone by measuring the temperature of the thread at the point where the neck is desired to be positioned and when the neck moves away from its desired ICC position by changing one or more process parameters that affect the position of the neck on the basis of or in response to the temperature measurement whereby the neck is caused to return to its desired position and thereafter discharging the thread from the drawing zone.

By the term nee or neck portion it is meant a portion of the thread in which, as a result of the deformation to which the thread is subjected, such an amount of drawing heat is released that in the thread portion a measurable change in temperature takes place along the thread.

One process parameter that affects the position of the neck is the ratio of the speed at which the thread is discharged from the drawing zone to the speed at which the thread is supplied thereto. If this ratio is increased to above that value at which the position of the neck is stationary, then the neck will move in a direction opposite to the direction of travel of the thread. If this ratio is decreased, the reverse takes place. Another process parameter by which the position of the neck maybe affected is the speed at which the thread is supplied to the drawing zone. If the supply speed is increased to above that value at which the position of the neck is stationary, then the neck will move in the direction of travel of the thread. And if the supply speed is decreased, then the neck will move in a direction opposite to the direction of travel of the thread.

However, for localizing the neck portion in the thread, it is preferred touse a process in which it is not necessary for the above-mentioned process parameters to be changed. A particularly effective and novel embodiment of the process of this invention is characterized in that before the temperature of the thread is measured in the drawing zone, the thread passes through a heated zone, and the temperature of the heated zone serves as a process parameter by which the position of the neck is affected, i.e., changed to the desired position.

The process according to this invention is particularly suitable to be used in the spindrawing of a thread. In this case the thread is subjected to drawing immediately after it has been spun, so that drawing is carried out at relatively high speeds, which would form an obstacle for the use of a drawpin.

With the drawing of threads of heavy denier, in particular with the spindrawing of such threads, it may appear that the thread before passing a thermocouple or other temperature sensing means will have to be cooled in a relatively vigorous manner to prevent the neck from locating too far upstream. It was found that this could be avoided with an embodiment of the process characterized in that the thread in the drawing zone, after formation of the neck, is passed over at least one friction member.

This invention is also directed to the use of an apparatus for drawing a thermoplastic thread. The apparatus utilized comprises feed means for feeding the thread to a drawing zone, discharge means for discharging the thread from the drawing zone at a rate that is higher than the feed rate of the thread, and control means for localizing the neck portion of the thread in the drawing zone, the control means including a temperature sensing element or means for measuring the temperature of the thread at the point where the neck portion of the thread is desired to be positioned, and a means cooperating with the temperature sensing means for affecting the position of the neck portion of the thread.

A preferred embodiment of this apparatus utilized is further characterized in that the means for affecting the position of the neck portion comprises a heating device or means with the aid of which the temperature of the thread can be changed before it passes the temperature sensing means, and an automatic controller having its input connected with the temperature sensing means and its output with the heating device.

The heating device used may be a heated body, e.g., a hot plate, which is positioned between the temperature sensing means and the feed means for supp-lying the thread to the drawing zone.

A very suitable apparatus is obtained if a heated roll over which the thread is passed is used as the device for heating the thread. For this purpose use may with advantage be made of the feed roll, which supplies the thread to the drawing zone and which bounds the drawing zone in combination with the draw roll.

This invention is also concerned with an embodiment of the apparatus utilized, which is particularly suitable for spindrawing of a thermoplastic thread and which is provided with at least one feed roll for feeding the thread to a drawing zone and one draw roll for discharging the thread from the drawing zone at a speed which is greater than the speed at which the thread is fed to the drawing zone. This embodiment of the apparatus is further characterized in that, in the drawing zone, between the temperature sensing means and the draw roll there is provided a friction member with which the thread is brought into slipping contact.

This invention also is directed to the threads manufactured by the heretofore described drawing process.

The invention will be further described with reference to the accompanying drawings, in which:

FIG. 1 is a schematic view of a thermoplastic thread drawing apparatus according to the invention;

FIG. 1A shows an enlarged view of the thermoplastic thread draw neck in FIG. 1, and

FIG. 2 shows another embodiment of the drawing apparatus of the invention for use in the spindrawing of polyamide yarn.

In FIG. 1, the reference numeral 1 designates a thermoplastic thread which is fed to a drawing zone bounded by an electrically-heated, driven feed roll 2 and a driven draw roll. The thread makes a few wraps around the rolls 2, 3 and the associated separator rolls 4, 5, respectively. Drawing takes place because the draw roll 3 imposes a speed on the thread 1 which is higher than that imposed by the feed roll 2. It will be recognized that in such drawing the thread speed shows a gradient in the drawing zone. At this velocity gradient the cross-sectional area of the thread, under the influence of plastic deformation, is strongly changed over a distance which is often relatively short. The thread portion in which this steep velocity gradient occurs (with the resulting decrease in cross-sectional area) is the heretofore described nec or neck portion (see FIG. 1A).

Besides a velocity gradient there occurs a temperature gradient in the drawing zone. This gradient is due to the heat liberated during the strong deformation to which the thread is subjected in the neck. The resulting rise in temperature in the neck may be many tens of degrees centigrade. Viewed in the direction of travel of the thread, the surface temperature of the thread near the neck first shows a relatively sharp increase to a certain maximum value, which is attained approximately at the neck, and then shows a gradual decrease. It therefore follows that the curve of the temperature gradient before the maximum is steeper than thereafter.

For the purpose of localizing the neck in the drawing zone, in accordance with this invention, a thread guide 6 with a built-in thermocouple is provided. The thermocouple is connected with an automatic controller or means 7, which regulates the electric heating of the feed roll 2. The connections of the controller 7 with the thermocouple and the electric heating device of the feed roll 2 are referred to by the reference numerals 8 nd 9, respectively.

Localization of the neck is effected in the following manner. When the neck is positioned between the feed roll and the thermocouple, and close to the thermocouple,

then the thermocouple will register a high temperature of the thread surface. The controller 7 responds to the indication of a high temperature by the thermocouple in that the controller reduces the heating of the feed roll 2. To this end the electric heating device may, for instance, entirely or partly be switched off. The resulting fall in temperature of the feed roll 2 leads to a decrease of the thread temperature, so that the neck moves in the direction of the thermocouple. When the neck passes the thermocouple, the thermocouple registers a falling thread temperature. As a result, the controller 7, in cooperation with the heating device of the feed roll 2, increases the temperature of this roll, so that the neck will move in the opposite direction. In this way the automatic control loop formed by the thread, the thermocouple, the automatic controller and the heated feed roll keeps the neck in the desired position.

On the drawing portion of the spindraw apparatus shown in FIG. 2, a -filament industrial nylon-6 yarn is in a continuous process subjected to drawing, relaxing and winding. The yarn 1, which issues from a spinning apparatus (not shown), successively passes a feed roll 2' with separator roll 4, a fixedly mounted hot plate 10, a thread guide 6 with built-in thermocouple, a driven roll 11, a draw roll 3' with driven separator roll 5' (both of which are heated), a pair of driven rolls 12, 13, and a grooved drum 14, and is then wound into a package 15, which is driven at a constant circumferential speed by a friction roll 16. The circumferential speed of the roll 11 is equal to that of the roll 2', so that the yarn 1' slips on the roll 11. This insures that the yarn is subject to friction, as a result of which a tension gradient occurs therein. The magnitude of the tension gradient caused by the roll 11 is also determined by the dilference between the yarn speed and the circumferential speed of the roll 11. With the embodiment described here the roll 11 is not provided with a heating device; the roll 11 acts as a cooling member for the nylon yarn.

Just as with the afore-described drawing apparatus of FIG. 1, the thermocouple in the thread guide 6 is connected with an automatic controller 7, which is connected to a heating device for the yarn 1. With the spindraw apparatus shown in FIG. 2 the heating .levice is not formed within the feed roll 2' but rather by the plate 10.

When the neck is positioned near the thermocouple or temperature sensing means in the thread guide 6, between the guide and the roll 11, then the thermocouple will register a relatively low yarn temperature. The automatic controller 7 now raises the temperature of the plate 10. As a result, the temperature of the as yet undrawn yarn is increased, so that the neck being formed will move in the direction of the thread guide. The drawing heat is now developed closer to the thermocouple so that it will register a rising yarn temperature. At a given moment the registered yarn temperature will be such that the controller 7 effects a decrease of the temperature of the plate 10, so that the neck will ultimately start to move in the opposite direction. In this way the neck moves backwards and forwards in the area around the thread guide 6. The frequency and the amplitude of its movement relative to the thread guide 6 are determined by various factors such as the speed of the yarn between the plate and the thermocouple, the transfer functions of the temperature sensing means, the controller and the hot plate 10, and the heat transfer from the plate to the yarn.

Instead of the heated plate 10 a heated roll may be used. To this end, for instance, the feed roll 2 may be provided with a heating device.

The process of this invention will be further understood from the following example:

EXAMPLE Using a spindraw apparatus with a drawing arrangement of the same type shown in FIG. 2, except that the plate 10 is replaced by a heated roll 2 the heating device Rolls 3 Rolls 12 Conditions Roll 2 Roll 11 and and 13 Circumferential speed (meters per minute) 400 400 1, 920 1, 880

Tempe1'ature, C 40-45 100 220 100 It will be appreciated that the drawn yarn was remarkable for its relatively high denier uniformity.

The yarn need not necessarily be heated by contacting it with a heated element. The heat transfer may just as well take place by radiation. Or, prior to passing the thermocouple or other temperature sensing means, the yarn may be guided through a heated liquid or subjected to the action of a gas stream of a predetermined temperature. It should be added that for localizing the neck not only heating but also cooling of the yarn may be considered. For instance, when the neck is positioned just before the thermocouple (i.e., left of the thermocouple in the guide 6 shown in FIG. 2), it may be moved towards the thermocouple by cooling the yarn. Neck localization can also be realized by a combination of heating and cooling. When the neck is positioned just before the thermocouple (i.e., the measured temperature is high), the yarn is cooled down, and when it is positioned after the thermocouple (i.e., the measured temperature is low), the yarn is heated for the purpose of increasing its temperature.

In addition to the process parameter mentioned above, it will be appreciated that other process parameters that affect or influence the position of the neck include, inter alia, the temperatures of the rolls 11, 3' and 5, as well as the angle of wrap of the yarn around the roll 11, and the difference between the circumferential speed of the roll 11 and the yarn speed. Also the roughness of the running surfaces of the roll 11 and of the other rolls alfec'ts the position of the neck. If the roughness of the running surfaces is not uniform in the axial direction of the rolls, the position of the neck may be influenced by displacing the yarn in the axial direction across the running surfaces. In the spindrawing process also the spinning temperature is a process parameter that affects the position of the neck.

It will be also appreciated that the process according to the invention may be applied to all synthetic linear polymers such as polyamides, e.g., nylon-6, nylon 6.6, and the 6 like, polyesters, e.g., polyethylene terephthalate and polypivalolactone, and the like, for which the above-described neckdrawing process is at the neck attended with a temperature gradient of measurable magnitude.

What is claimed is:

1. A process for drawing a thermoplastic synthetic linear polymeric thread, comprising:

(a) feeding the yarn to a drawing zone;

(b) axially loading the thread in the drawing zone with suflicient tension to plastically deform the thread over a relatively short neck portion whereby considerable heat due to said deformation is released from said portion;

(0) sensing the heat released from said portion of thread near a desired drawing zone position and manipulating at least one process parameter affecting said portion to maintain said portion at the desired drawing zone position; and

(d) thereafter discharging the thread from the drawing zone.

2. The process of claim 1 in which prior to measuring the temperature of said thread, the thread is passed through a heated zone whereby the temperature of the heated zone serves as the process parameter that affects the position of the neck portion in the thread.

3. A process for the spindrawing 9f a thread in which the thread is drawn by the drawing process of claim 1.

References Cited UNITED STATES PATENTS 3,342,975 9/1967 Carr 34-148 X 2,930,102 3/ 1960 Hitchin et al 264-40 FOREIGN PATENTS 781,105 3/1968 Canada 264-290 964,369 7/1964 Great Britain 264-290 OTHER REFERENCES Billmeyer, Fred W. Texbook of Polymer Science, New York, Interscience (1964), pp. 164-171.

Marshall, I. and A. B. Thompson. The Cold Drawing of High Polymers, in Proc. Roy. Soc. (London), series A, No. 1147, vol. 221, Feb. 9, 1954, pp. 541-557.

Vincent, I. The Necking and Cold-Drawing of Rigid Plastics, In Polymer, vol. 1, No. 1, March 1960, pp. 7-19.

PHILIP E. ANDERSON, Primary Examiner US. Cl. X.R.

18-1 FT, 2HA; 264-68, 290 N, 290 T, 34 S 

